The object of this project is to evaluate the role of myc-gene expression in influencing biological and biochemical characteristics of small carcinoma of the lung (SCCL). SCCL can be histopathologically categorized into at least two forms. The predominant form(s) have long been recognized as the small (oat) cell and intermediate subtypes. Another less common form is the mixed small cell/large cell morphologic type. Recently continuous cultures of SCCL have also been divided into two major forms, i.e., 1) the classic form and 2) the variant form. These two types have different biochemical and biological characteristics and have been correlated with the small cell/intermediate cell and small cell/large cell histopathologic forms in patients respectively. Of particular interest has been the observation that practically all the variant cell lines have significant amplification of the c-myc or the related n-myc genes while this rarely occurs in the classic cell lines. The specific aims of this investigation will be to: 1) cotransfect SCCL cells which are not expressing the c-myc gene with cloned v-myc or c-myc sequences and vector-Ecogpt DNA using the calcium phosphate transfection method; 2) select cells containing the transfected genes with the mycophenolic acid selection method; 3) clone the transfected cells and determine the relative expression of the myc gene in these transfected clones by Southern and Northern blotting of DNA and RNA respectively and hybridization with a c-myc probe; and 4) compare the populations of cells containing the transfected activated myc-gene for: (a) proliferative capacity; (b) colony forming capability; (c) tumorigenicity in nude mice; and (d) hormone as well as L-DOPA decarboxylase production with the original cell line which did not express the myc-gene. These investigations will lead to a much better understanding of the role of c-myc expression in SCCL and whether or not it is significantly related to important biological and functional characteristics of this tumor. (X)